function [aux_data]=fix_aux_data_M_PB(aux_data,ExpID)

% in the beginning running and PB during M session were recorded on one
% channel (2)
M_PB_aux_boundary=5566;

if ExpID<M_PB_aux_boundary
    disp('This is old data - now fixing aux_data (M-PB)')
    shutter_opening_times=find((diff(aux_data(4,:))>2));
    
    if shutter_opending_times(1)>10000
        disp('CRITICAL WARNING! fix_aux_data_M_PB: something is wrong');
    elseif length(shutter_opending_times)<2
        disp('CRITICAL WARNING! fix_aux_data_M_PB: something is wrong');
    end
    
    aux_data(7,1:shutter_opening_times(2))=aux_data(2,1:shutter_opening_times(2));
end

    